An environmentally friendly lawn infill granule and its preparation method

Abstract

This invention discloses an environmentally friendly lawn infill granule and its preparation method. The environmentally friendly lawn infill granule is made from raw materials comprising a biodegradable polymer A, a biodegradable polymer B, a plasticizer, a peroxide initiator, and a co-crosslinking agent; the biodegradable polymer A is PLA or PPC, the biodegradable polymer B is PBAT or PBS, the plasticizer is ethyl cashew nut shell powder or epoxy ethyl cashew nut shell powder, and the co-crosslinking agent is triallyl isocyanurate. The infill granules prepared by this invention possess the elasticity and resilience of rubber, and their mechanical properties, hardness, and color are controllable, making them suitable as lawn infill granules.

Description

Technical Field

[0001] This invention relates to a novel environmentally friendly lawn filler granule and its preparation method, belonging to the field of polymer materials research. Background Art

[0002] Artificial turf originated in the 1960s to solve the maintenance problems of natural lawns. It is mainly composed of grass fibers, a backing fabric, and adhesive. Initially, nylon fibers were used, but later materials such as polypropylene and polyethylene were adopted. Its advantages include low maintenance costs, no climate limitations, and high durability. However, it also has limitations such as high surface temperature, poor feel, and room for improvement in environmental friendliness.

[0003] Infill granules emerged with the development of artificial turf technology, initially using sand, later incorporating rubber granules, and so on. Infill granules enhance the elasticity, cushioning, and stability of the turf, reducing sports injuries, and also improving drainage and aeration. Currently, there are three main types of artificial turf infill granules on the market: ① black waste tire infill granules; ② vulcanized EPDM infill granules; ③ thermoplastic elastomer granules. Due to its low cost, waste tire infill granules are the most widely used both domestically and internationally. However, black waste tire infill granules contain carcinogenic polycyclic aromatic hydrocarbons, facing significant environmental pressure; vulcanized EPDM granules are thermosetting materials, cannot be recycled, and have a rubbery odor; therefore, thermoplastic elastomers have become the best choice for infill granules. Summary of the Invention

[0004] The purpose of this invention is to provide an environmentally friendly lawn infill granule and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] In a first aspect, the present invention provides an environmentally friendly lawn infill granule, which is made from raw materials comprising biodegradable polymer A, biodegradable polymer B, plasticizer, peroxide initiator, and co-crosslinking agent. Based on the total weight of the biodegradable thermoplastic phase and the biodegradable rubber phase being 100%, the weight percentages of biodegradable polymer A and biodegradable polymer B are 30%-40% and 60%-70%, respectively, and the weight amount of plasticizer is equal to the total weight of biodegradable polymer A and biodegradable polymer B. The amount used is 10%-20%, and the weight of the peroxide initiator and the co-crosslinking agent is 0.1%-1% and 0.2%-2% of the weight of the biodegradable polymer B, respectively; the biodegradable polymer A is PLA (polylactic acid) or PPC (polypropylene carbonate), the biodegradable polymer B is PBAT (polybutylene adipate / terephthalate) or PBS (polybutylene succinate), the plasticizer is ethyl cashew nut shell powder or epoxy ethyl cashew nut shell powder, and the co-crosslinking agent is TAIC (tracene propyl isocyanurate).

[0007] Since the glass transition temperature of PBAT or PBS is only around -30°C, these two materials are in a highly elastic state at room temperature and should be elastomers, but they have large irreversible deformations. This invention achieves better deformation recovery by adding plasticizers and using peroxide initiators to crosslink their internal structure into a network. The thermoplastic phase is replaced by PLA or PPC to provide structural support. During dynamic vulcanization, the crosslinking agent also forms PLA-PBAT graft products at the interface, improving its mechanical properties. Thus, a thermoplastic dynamic vulcanized rubber (TPV) with adjustable mechanical properties and hardness is obtained to serve as infill particles for artificial turf.

[0008] Preferably, the peroxide initiator is BIBP (bis-tert-butyl peroxide) or DCP (diisopropyl peroxide).

[0009] Preferably, the peroxide initiator and the co-crosslinking agent are used at weights of 0.1%-0.3% and 0.2%-0.6% of the biodegradable rubber phase, respectively.

[0010] Secondly, the present invention also provides a method for preparing the environmentally friendly lawn infill granules described in the first aspect, comprising the following steps:

[0011] S1: Add peroxide initiator and crosslinking agent to polymer B, mix evenly at room temperature in a high-speed mixer, extrude and granulate in a twin-screw extruder, and air-cool and pelletize to obtain premix;

[0012] S2: Weigh polymer A and premixed material according to the proportion, mix them in a high-speed mixer, add the mixture to the hopper of a twin-screw extruder, and at the same time, use a constant flow pump to pump plasticizer into the twin-screw extruder through a vacuum port. Extrude and granulate through the twin-screw extruder, and air-cool and pelletize to obtain environmentally friendly lawn filling granules.

[0013] Since the peroxide initiator reacts with both polymer A and polymer B, the present invention first adds the crosslinking agent to polymer B and mixes it evenly without causing a reaction. In the second step, it is then dynamically vulcanized simultaneously with polymer A and plasticizer to ensure that the crosslinking reaction occurs in large quantities in the rubber phase represented by polymer B, so as to provide elasticity.

[0014] Preferably, in step S1, the conditions in the twin-screw extruder are set as follows: temperature 110℃-130℃, screw speed 100-150rpm.

[0015] Preferably, in step S2, the conditions in the twin-screw extruder are set as follows: temperature 150℃-180℃, screw speed 100-150rpm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. Both the thermoplastic phase and the rubber phase of this invention are biodegradable polyesters, and the plasticizer is also a bio-based plasticizer. It can degrade on its own after use, waste, or loss. It is environmentally friendly, green, and non-toxic, and will not produce the release or volatilization of harmful substances.

[0018] 2. Although this invention is made of plastic, it has the elasticity and resilience of rubber, and its mechanical properties, hardness, and color are adjustable. It can be used as filler granules for lawns in some high-end venues, paving the way for reducing pollution caused by non-recyclable rubber. Attached Figure Description

[0019] Figure 1 Cyclic tensile diagrams of the filler particles prepared in Comparative Example 1 and Examples 1-4.

[0020] Figure 2 TEM images of the filling particles prepared in Examples 1, 2 and 4, where (a), (b) and (c) correspond to the products of Examples 1, 2 and 4, respectively. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0022] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0023] In the following examples, the PLA used was REVODE101 (high D-type lactic acid content, non-crystallizing) purchased from Zhejiang Hisun Biomaterials Co., Ltd., and the PBAT used was TH-801 from Xinjiang Lanshan Tunhe Co., Ltd. The plasticizer (epoxidized cashew phenol ethyl ester) used was purchased from Jiangsu Union Chemical Co., Ltd. The initiator BIBP and the crosslinking agent TAIC were both commercially available industrial-grade reagents.

[0024] Comparative Example 1

[0025] Raw material composition: PLA 30wt%, PBAT 70wt%, epoxidized cashew phenol ethyl ester 20wt% (percentage of total mass of PLA and PBAT).

[0026] PLA and PBAT are weighed in proportion and mixed in a high-speed mixer. The resulting mixture is fed into the extruder through the hopper of a twin-screw extruder (SHJ20, Nanjing Juli Chemical Machinery Co., Ltd.). At the same time, a constant flow pump injects plasticizer into the extruder through the vacuum port of the twin-screw extruder. The mixture is extruded into strips by the twin-screw extruder, and then air-cooled and pelletized to obtain lawn filling granules.

[0027] The specific temperatures of the twin-screw extruder (from feed inlet to die) are as follows: 150℃, 160℃, 170℃, 180℃, 180℃, 170℃, 165℃, 155℃, 155℃; the rotation speed is 150 rpm. The constant flow pump flow rate is set to 75 ml / min.

[0028] Example 1

[0029] Raw material composition: PLA 30wt%, PBAT 70wt%, epoxidized cashew phenol ethyl ester 20wt% (percentage of total mass of PLA and PBAT). BIBP and TAIC are used at 0.1%wt and 0.2%wt of PBAT mass, respectively.

[0030] S1: Weigh BIBP and TAIC, add them to PBAT, and mix for 5 minutes at room temperature in a high-speed mixer; extrude and granulate in a twin-screw extruder, then air-cool and pelletize to obtain PBAT premix. The specific temperatures of the twin-screw extruder (from feed inlet to die) are as follows: 120℃, 125℃, 125℃, 130℃, 130℃, 130℃, 125℃, 120℃, 120℃; the speed is 100 rpm.

[0031] S2: Weigh PLA and PBAT premixes according to the specified ratio and mix them thoroughly in a high-speed mixer. The resulting mixture is fed into the extruder through the hopper of a twin-screw extruder. Simultaneously, a plasticizer is pumped into the extruder through the vacuum port of the twin-screw extruder using a constant flow pump. The mixture is then extruded and granulated using the twin-screw extruder, followed by air cooling and pelletizing to obtain environmentally friendly lawn infill granules. The specific temperatures of the twin-screw extruder (from feed inlet to die) are as follows: 150℃, 160℃, 170℃, 180℃, 180℃, 170℃, 165℃, 155℃, 155℃; the rotation speed is 150 rpm. The constant flow pump flow rate is set to 75 ml / min.

[0032] Example 2

[0033] Same as Example 1, except that the amounts of BIBP and TAIC are 0.2%wt and 0.4%wt of the mass of PBAT, respectively.

[0034] Example 3

[0035] Same as Example 1, except that the amounts of BIBP and TAIC are 0.3%wt and 0.6%wt of the mass of PBAT, respectively.

[0036] Example 4

[0037] Same as Example 1, except that the amounts of BIBP and TAIC are 0.4%wt and 0.8%wt of the mass of PBAT, respectively.

[0038] Performance Testing and Results Analysis

[0039] Mechanical properties testing

[0040] Tensile tests were performed on a universal testing machine according to ASTM D882-12. The samples were cut into dumbbell-shaped strips, 75 mm long, 4 mm wide at parallel sections, and 2 mm thick. All samples were placed at 20°C and 50% RH for 24 hours. The mechanical properties of the strips were tested at a tensile rate of 100 mm / min at room temperature. Five samples were measured in each group, and the results were arithmetically averaged. The results are shown in Table 1.

[0041] With a fixed strain of 50%, the samples were subjected to cyclic tensile tests at 50°C for 5 cycles. The results are shown in Table 2.

[0042] Table 1 Mechanical Properties

[0043]

[0044] The crosslinking agent content has a significant impact on the mechanical properties of TPV. As shown in Table 1, we can see that the tensile strength of the PLA / PBAT blend without the addition of a crosslinking system is very low, only 7.1 MPa. There are two reasons for such low strength. First, the plasticizer has an effect. Small molecule plasticizers are embedded in the molecular chains, separating them and greatly increasing the mobility of the molecular chains, which leads to a significant decrease in modulus and strength. This is one of the reasons why the strength of the TPV system is generally low. Second, the incompatibility between the PLA and PBAT systems results in weak intermolecular bonding forces, and voids often form between the two phases, significantly affecting the strength of the blend. In this work, the crosslinking agent is pre-dispersed uniformly in the PBAT phase. During dynamic vulcanization, the crosslinking agent molecules on its surface react with both PLA and PBAT simultaneously, thereby strengthening the interfacial compatibility and significantly improving the mechanical properties. The tensile strength of Examples 1-3 is around 9.3 MPa, while the tensile strength of Example 4 is only 7.3 MPa, and the elongation at break is also significantly reduced. It can be inferred that this is due to the performance loss caused by excessive crosslinking of PBAT. Therefore, a suitable degree of crosslinking can maintain the optimal performance of PLA / PBAT-based TPV.

[0045] Table 2 Permanent Tensile Deformation

[0046] Tensile permanent deformation (%) at 50% deformation Comparative Example 1 54.0 Example 1 26.3 Example 2 23.3 Example 3 28.7 Example 4 29.3

[0047] To investigate the deformation recovery capability of PLA / PBAT, cyclic stress-strain tests were conducted at 50% strain. The results are as follows: Figure 1 As shown in Table 2, pure PLA / PBAT blends exhibit slippage after molecular chain stretching. Lacking crosslinking components, they lack recovery capability, resulting in significant tensile permanent deformation. Samples with added plasticizers show partial recovery due to the lubricating effect of the plasticizer, but the effect is not ideal. With the addition of a crosslinking agent, the crosslinking component acts as an elastomer, providing elastic recovery and achieving lower tensile permanent deformation. The stress performance at 50% strain varies among samples due to different amounts of crosslinking agent. The increased stress at crosslinking agent content above 0.2% is due to the increased crosslinking density; the molecular chains are less prone to slippage compared to samples with lower crosslinking agent content, resulting in more broken molecular chains at the same strain, making it more difficult to return to the initial state and thus increasing permanent deformation.

[0048] As is well known, TPV's elasticity is lossy. Unlike rubber or other elastomers, it does not have 100% deformation recovery. After the first stretch, there is a significant loss, but the loss will gradually decrease with the number of cycles. This is because during the first stretch, the PLA molecular chains, which are the plastic phase, break. This is an irreversible deformation. In subsequent stretches, the number of broken PLA molecular chains will gradually decrease until an equilibrium is reached.

[0049] Compression permanent deformation

[0050] The compression set of the sample was tested according to GB / T 7759.1-2015. Since the outdoor temperature was not high, we combined the usage scenario and the conditions were 40℃, 22h, and 25% strain.

[0051] Table 3 Compression Permanent Deformation

[0052]

[0053]

[0054] Where h0 is the initial height of the sample, h1 is the height of the sample after recovery, and h s This is the limiter height.

[0055] Compression set is an important parameter of TPV (Total Product Value), reflecting the elasticity and deformation recovery ability of a product. It is a commonly used testing method for rubber and thermoplastic elastomers. From the results in Table 3, we can see that Comparative Example 1, without crosslinking agent, has the highest compression set at 31.7%. However, with the increase of crosslinking agent content, a crosslinking network gradually forms in the PLA / PBAT blend, restricting the relative slippage between molecular chains and providing elasticity to the sample. When the product is subjected to external force, internal counter-stress is generated, and after the external force is removed, the product recovers through the crosslinking network, resulting in a reduction in compression set, reaching 14.4%, which is half that of Comparative Example 1.

[0056] Resilience and hardness

[0057] The springback rate and hardness of the samples were tested according to GB / T 1681-2009 and GB / T 23651-2009, respectively.

[0058] Table 4 Resilience and Hardness

[0059] rebound rate hardness Comparative Example 1 43.2％ 93.0 Example 1 52.9％ 73.0 Example 2 48.5％ 72.0 Example 3 49.4％ 75.0 Example 4 46.6％ 72.5

[0060] Table 5 Resilience and Hardness of Some Common Rubbers

[0061] rebound rate hardness Natural rubber Around 70% 30-90 Styrene-butadiene rubber 40％-50％ 40-95 butadiene rubber 70％-95％ 30-80 Chloroprene rubber 30％-50％ 40-90 silicone rubber 50％-60％ 20-90 Nitrile rubber 20％-50％ 40-95

[0062] Resilience and hardness are also important parameters in rubber testing. Table 4 shows the resilience and hardness of each comparative example and embodiment. Comparing the resilience and hardness of some common rubbers, we can see that the resilience is very close to that of rubber, while the hardness is determined according to the needs of different scenarios. The hardness range of various rubbers is very wide. The hardness of the embodiments of this invention is generally around 72, which is relatively soft. Based on these two data points, this invention can basically replace rubber particles in terms of resilience and hardness.

Claims

1. An environmentally friendly lawn infill granule, characterized in that: The environmentally friendly lawn infill granules are made from raw materials comprising biodegradable polymer A, biodegradable polymer B, plasticizer, peroxide initiator, and co-crosslinking agent. Based on the total weight of biodegradable polymer A and biodegradable polymer B as 100%, the weight percentages of biodegradable polymer A and biodegradable polymer B are 30%-40% and 60%-70%, respectively. The weight of the plasticizer is 10%-20% of the total weight of biodegradable polymer A and biodegradable polymer B. The weights of the peroxide initiator and co-crosslinking agent are 0.1%-1% and 0.2%-2% of the weight of biodegradable polymer B, respectively. The biodegradable polymer A is PLA, the biodegradable polymer B is PBAT or PBS, the plasticizer is ethyl cashew nut shell powder or epoxy ethyl cashew nut shell powder, the co-crosslinking agent is triallyl isocyanurate, and the peroxide initiator is bis-tert-butyl peroxide. The environmentally friendly lawn infill granules are prepared by a method including the following steps: S1: Add the peroxide initiator and crosslinking agent to polymer B, mix them evenly at room temperature in a high-speed mixer, and then extrude and granulate them in a twin-screw extruder. The conditions in the twin-screw extruder are set as follows: temperature 110℃-130℃, screw speed 100-150 rpm, and air-cooled pelletizing to obtain the premix. S2: Weigh polymer A and premixed material according to the proportion, mix them in a high-speed mixer, add the mixture to the hopper of a twin-screw extruder, and simultaneously pump plasticizer into the twin-screw extruder through a vacuum port using a constant flow pump. Extrude and granulate through the twin-screw extruder. The conditions in the twin-screw extruder are set as follows: temperature 150℃-180℃, screw speed 100-150 rpm, and air-cooled pelletizing to obtain lawn filling granules.

2. The environmentally friendly lawn infill granules as described in claim 1, characterized in that: The peroxide initiator and the co-crosslinking agent are used at weights of 0.1%-0.3% and 0.2%-0.6% of the biodegradable polymer B, respectively.

3. A method for preparing environmentally friendly lawn infill granules as described in claim 1 or 2, characterized in that: The preparation method includes the following steps: S1: Add the peroxide initiator and crosslinking agent to polymer B, mix them evenly at room temperature in a high-speed mixer, and then extrude and granulate them in a twin-screw extruder. The conditions in the twin-screw extruder are set as follows: temperature 110℃-130℃, screw speed 100-150 rpm, and air-cooled pelletizing to obtain the premix. S2: Weigh polymer A and premixed material according to the proportion, mix them in a high-speed mixer, add the mixture to the hopper of a twin-screw extruder, and simultaneously pump plasticizer into the twin-screw extruder through a vacuum port using a constant flow pump. Extrude and granulate through the twin-screw extruder. The conditions in the twin-screw extruder are set as follows: temperature 150℃-180℃, screw speed 100-150 rpm, and air-cooled pelletizing to obtain lawn filling granules.

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